Description

The roseate tern population in the UK experienced the most
dramatic decline of any seabird species between Operation Seafarer
(1969-70) and the SCR Census (1985-88). It also has one of the most
restricted ranges of any seabird around the British Isles, with
most of the population breeding in just a few colonies.
Consequently, the species is of high conservation concern and
is one of three red-listed seabirds in the United Kingdom.
Roseate terns have probably always been rare and localised in
the UK owing to their specialised foraging and nesting habitat
requirements. Driven to the brink of extinction by exploitation for
the millinery trade during the 19th century, the
population recovered through the early 20th century as a
result of protective legislation and management. Numbers peaked in
the late 1960s, but declined thereafter possibly due to poor
immature survival rates, and this may have been partially
attributable to deliberate trapping in the Ghanaian wintering
grounds. Factors such as predation and nesting habitat loss (due to
erosion, competition with gulls and/or disturbance) may have also
played a role.

Conservation efforts are directed towards education programmes
in the wintering areas in NW Africa and management of breeding
sites. However, recovery is evident only at the largest
colony, with smaller peripheral colonies declining to low levels or
being abandoned despite intensive efforts to maintain them.
Movements of birds among colonies within the metapopulation has
been an important determinant of regional population trends during
the past three decades. Therefore, maintaining or enhancing the
species range is likely to depend on conservation efforts to
promote growth of relict colonies, restore breeding at
abandoned sites, and create new colonies.

Conservation status

Roseate Tern is currently identified as a conservation priority
in the following:

International importance

The UK population figure was derived from data in Mitchell,
P.I., Newton, S.F., Ratcliffe, N.
and Dunn, T.E. (eds.) 2004. Seabird
Populations of Britain and Ireland.
Poyser, London. This was also the source of figures for the
Biogeographic and World populations.

UK population estimates and change 1969-2002 (census data)

Roseate terns are restricted to a small number of well-known
colonies in the UK, all of which have been counted near
annually since 1969, such that their populations are monitored in
more detail than any other seabird breeding here. Roseate
terns were surveyed during Seabird 2000 by systematically counting
all nests situated along transect lines set up through colonies.
Nests are usually hidden in long vegetation, among boulders, in
rabbit burrows or in nest boxes and so counts of AONs from a
vantage point will miss a large proportion of nests. The
species may move among colonies between years in response to
predation or habitat change and so, to avoid double-counting or
missing some pairs, all colonies were counted in 2000. During the
SCR Census (1985-88) counts were conducted in different years at
some colonies. In order to be comparable with Seabird
2000, only counts from the SCR Census conducted in
1986 were used; this was when the most comprehensive survey
coverage of colonies was achieved during the period 1985-88.

Operation Seafarer

(1969-70)

Seabird Colony Register

(1986)

Seabird 2000

(2000)

UK Population estimate (AON*)

955

323

56

% change since previous census

N/a

-66

-83

*AON = Apparently Occupied Nests

For census results for individual countries and Ireland, the
Channel Islands and the Isle of Man see under relevant
sections below.

Distribution/abundance

The Seabird
2000 census provides the most comprehensive recent
assessment of the distribution and abundance of breeding seabirds.
Numbers of roseate tern found in different regions, and a
map showing the locations and size of colonies, is provided in
the Seabird 2000 roseate
tern results page (PDF, 1.0 mb).

An
interactive map is available on the NBN Gateway, where you can
filter to display only the Seabird 2000 data. For more
recent, but less comprehensive, coverage view the distribution on
the NBN with all available contributing datasets.

Annual abundance and productivity by geographical
area

With reference to the regional
accounts below please note the following.

Breeding abundance:
graphs of abundance index with 95% CLs are only shown for a region
where the trend produced has been deemed accurate (see
methods of analysis). Where a trend was thought to be
inaccurate, graphs of abundance at major colonies in a
region may be shown instead, particularly if such colonies
hold greater than 10% of the regional population,
are monitored frequently and may thus help illustrate regional
population fluctuations outwith national censuses.
Occasionally, too few data have been collected regionally to
produce either of these.

Productivity: graphs
of productivity are only shown if analysis of breeding
success data produced a significant result for regional and/or
year effects (again see
methods of analysis). If results were not significant,
then a regional mean productivity value is given.
However, on some occasions too few data are
available from which to provide a meaningful average.
Furthermore, for 11 species where the quality of monitoring data
available was considered high, population viability analysis
was undertaken at the UK level and the results of this are
also reported.

Breeding abundance

The UK roseate tern population has undergone a long-term
decline, decreasing from 950 pairs in 1969-70 to 320 in 1985-88 and
falling further between 1986 and 1991, mostly due to mortality of
immature birds in their winter quarters in west Africa, which
reduced subsequent recruitment into the breeding population. On the
wintering grounds, boys trapped and killed mainly immature birds
for food, sport or profit, and while education programmes in the
late 1980s and early 1990s reduced mortality rates, these need
to be maintained or a resurgence in trapping is likely1.
Food supply in the species wintering grounds is also likely to have
affected immature survival rates. The above conservation
measures (and providing shelter and protection from avian predators
in the form of nest boxes at some colonies) have resulted in the UK
population starting to recover. Just 56 AON were recorded by
Seabird 2000 but this has now risen so that the UK population
numbered 113 AON in 2015. However, declines occurred
at all colonies, whilst recovery has mostly been confined to
just one main colony and, although numbers are increasing
there, full recovery of the UK population remains a long way
off.

Productivity

Although productivity was low in two
years in the late 1980s when the population
was declining, the number of chicks fledged in UK roseate tern
colonies has generally been moderate to high throughout the
reporting period. This is partly due to increased conservation
effort. Predation of chicks was the likely cause of low
productivity in 1987 and 1988, and poor weather affected west
coast colonies in 1990, but the cause of low productivity in
other years, e.g. 2008, 2010, 2013 and 2015 was not reported.

Population estimates and change 1969-2002 (census data)

Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

Population estimate (AON*)

134

18

14

% change since previous
census

N/a

-87

-22

* AON = Apparently Occupied Nests

Breeding abundance

Figure 1: Abundance of roseate tern on the
Forth Islands, 1986-2015.

The three national censuses show a large decline in roseate
numbers from 134 pairs in 1969-70 to a mere 14 pairs during Seabird
2000. In the Firth of Forth, the stronghold of the species in
Scotland, the decline recorded there since the late 1980s
was fairly steady, albeit with some fluctuation (Figure 1). Three
islands in the Forth formerly held colonies of roseate terns,
although the largest colony had effectively disappeared by the
early 1990s due to increased competition for nesting habitat with
herring gulls, and breeding at another isle
was sporadic. Only one colony has been active in recent years
but it too has disappeared due to flooding, predation and
disturbance. Elsewhere in Scotland, single pairs occasionally
frequent other tern colonies just maintaining its status as a
breeding species in the country. No records were submitted to the
SMP for 2015.

Productivity

Productivity data at Scottish colonies showed
no statistically significant variation over time, although was
low, averaging 0.34 chicks fledged per pair per
year between 1992 and 2007 (the last year for which the SMP
has data).

Population estimates and change 1969-2002 (census data)

Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

Population estimate (AON*)

355

34

36

% change since previous
census

N/a

-90

+6

* AON = Apparently Occupied Nests

Breeding abundance

In contrast to Scotland, the one extant roseate tern
colony in England, on Coquet Island (Northumberland), has fared
better. National census results show that a large decline
occurred throughout England between Operation Seafarer and the
Seabird Colony Register, both in terms of the number of
birds and number of colonies. Numbers have increased
since then, but the species is now confined to Coquet. The
rate of increase at this colony was slow at first (from 17 to
38 pairs between 1986 and 2000) but increased rapidly from
2000 onward, with numbers reaching 94 pairs in 2006.
However, the increase appears to have halted; numbers
between 2007 and 2015 varied between 70 and 111 pairs.
Active management on Coquet, via the provision of nestboxes for
shelter and protection from avian predators together with habitat
management, has undoubtedly helped the species thrive
there, perhaps to the detriment of other nearby colonies as
birds abandon them in favour of
Coquet.

Productivity

Figure 2: Trend
in productivity (no. of chicks fledged per pair)
of roseate tern at colonies in England, 1986-2015.
Based on SMP data; view the methods
of analysis (PDF 158 kb).

The productivity of roseate terns at colonies
in England shows no definitive trend. Mean productivity usually
lies below 0.90 chicks fledged per pair, in contrast to the
colonies in the Republic of Ireland which seldom fledge less than
1.00 chick per pair per year. Despite the low success, numbers in
England had been increasing (Figure 1), although breeding roseate
terns are now confined to just one colony (c. five
colonies known during 1985-88), with sporadic sightings at others
during the summer months.

Population estimates and change 1969-2002 (census data)

Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

Population estimate (AON*)

202

209

2

% change since previous
census

N/a

+3

-99

* AON = Apparently Occupied Nests

Breeding abundance

Figure 1: Abundance of roseate tern
at colonies in Wales, 1986-2015.

The decline in roseate tern numbers in Wales was steep after the
Seabird Colony Register, although prior to this numbers appeared
stable in contrast to the populations of other countries in the
British Isles. By 1991, very few breeding pairs were left, and
although there was a slight increase in 1993 and 1994, numbers soon
decreased again and have never recovered. Ringing studies
showed the decline was apparently due to terns deserting colonies
in Wales (and Northern Ireland) and emigrating to those in the
Republic of Ireland where active management had created sites
of higher quality. No roseate terns have nested in
Wales during nine of the last 10 years although one pair was
present at a colony in 2014 and 2015 and bred successfully.

Productivity

Productivity data at Welsh colonies showed no
statistically significant variation over time, averaging
0.68 chicks fledged per pair per year between 1987 and
2006 (the last year for which the SMP has data).

Population estimates and change 1969-2002 (census data)

Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

Population estimate (AON*)

264

62

4

% change since previous
census

N/a

-76

-94

* AON = Apparently Occupied Nests

Breeding abundance

Figure 1: Abundance of roseate tern at
three colonies in Northern Ireland, 1986-2015.

In common with Scotland and England, the roseate tern population
of Northern Ireland declined between Operation Seafarer and the
Seabird Colony Register, although the nearby Welsh population was
stable during this period. Then, in conjunction with Welsh
colonies, a steep fall in numbers occurred so that few were left
breeding by 1991. Emigration of birds to higher quality breeding
sites in the Republic of Ireland was at least part of the reason
for the decline. Since the mid 1990s, the population has fluctuated
without showing any prolonged recovery, but, as of 2003, has
once more declined toward zero with just a single pair recorded
nesting each year from 2009 to 2013, with two pairs present in 2014
and one in 2015. Single non-breeding birds have also been recorded
at some other sites in recent years.

Productivity

There is no statistically significant
variation over time in productivity data collected at colonies in
Northern Ireland which were slightly more successful than Scottish
colonies. Roseate tern productivity averaged 0.56 chicks
fledged per pair per year between 1991 (the first year in the
SMP with data) and 2015.

After the near ubiquitous decline recorded throughout the
British Isles between Operation Seafarer and the Seabird Colony
Register, roseate tern numbers in the Republic of Ireland have
undergone a healthy increase which continues to the present.
However, breeding is now confined to three colonies one
of which holds almost 90% of the population with only a few pairs
at another. As on Coquet (England), the provision of nestboxes, in
conjunction with other management prescriptions (e.g. predator
control and habitat creation) have been of benefit to
the survival of the species. Over 1,400 roseate terns were
recorded nesting in 2014. Numbers in 2014 were well above those
recorded by Seabird 2000, and the SCR census before it, and were
approaching levels recorded by Operation Seafarer in 1969/70. No
data from the Republic of Ireland were submitted to the SMP for the
2015 breeding season.

Productivity

Figure 2: Trend
in productivity (no. of chicks fledged per pair)
of roseate tern in the Republic of Ireland, 1986-2014.
Based on SMP data; view the methods
of analysis (PDF 158 kb).

Roseate terns at colonies in the Republic of Ireland have
generally been quite productive over the years, usually
fledging more than one chick per pair each year. However, in
1997, 1998, 2008, 2012 and 2014 productivity
was lower than this, largely as a result of losses of
eggs and chicks due to poor weather. No data from the Republic of
Ireland were submitted to the SMP for the 2015 breeding season.

Population estimates and change 1969-2002 (census data)

Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

Population estimate (AON*)

1,693

289

738

% change since previous
census

N/a

-83

+155

* AON = Apparently Occupied Nests

Breeding abundance

Counting roseate terns only takes place at a
small number of colonies, limited data is therefore available for
produce a reliable abundance trend for Ireland. Within Ireland, the
roseate tern nests mainly in the Republic of Ireland. Thus,
all data and text for the Republic of
Ireland is also pertinent to the status of the species
for the whole of Ireland. No data from the Republic of Ireland
were submitted to the SMP for the 2015 breeding season.

Productivity

Figure 2: Trend
in productivity (no. of chicks fledged per pair)
of roseate tern throughout Ireland, 1986-2015. Based on
SMP data; view the methods
of analysis (PDF 158 kb).

Unsurprisingly, the trend shown above for
All-Ireland closely matches that shown for the Republic of Ireland,
where the majority of data have been collected over the years,
albeit with slightly lower average annual values. Losses of
eggs and chicks due to poor weather were responsible
for at least some of relatively low values recorded
e.g. in 1998 and 2008.

Roseate tern does not breed on the Isle of
Man.

Roseate tern does not breed on the
Channel Islands.

UK phenology, diet, survival rates

No data have been collected as part of the Seabird Monitoring
Programme.

Partners

Data have been provided to the SMP by the generous contributions
of its partners, other organisations and volunteers throughout
Britain and Ireland. Partners to the SMP are: BirdWatch Ireland;
The British Trust for Ornithology; Centre for Ecology and
Hydrology; Natural Resources Wales; Department of Environment,
Food and Agriculture (Isle of Man); Department of Environment,
Heritage and Local Government (Republic of Ireland); States of
Guernsey Government; JNCC; Manx Birdlife; Manx National Heritage;
The National Trust; National Trust for Scotland; Natural England;
Northern Ireland Environment Agency; The Royal Society for the
Protection of Birds; Scottish Natural Heritage; Seabird Group;
Shetland Oil Terminal Environmental Advisory Group; Scottish
Wildlife Trust. More about the SMP partners >>